The aim of this project is to study the function and structure of subcutaneous adipose tissue during the early postnatal period in abnormal human newborns in comparison with normal fullterm neonates. Investigations use samples of adipose tissue (10 to 40 mg each) obtained from the gluteal region by a needle biopsy technique. This site can be sampled easily withou significant risk. Methods include study of substrate concentrations and interconversions using labeled materials, of the activity of several enzymes, and of cell morphology including ultrastructure using the electron microscope. Small fragments of tissue, isolated suspensions of adipose cells, and subcellular components (mitochondria) are examined. Basic data obtained using these methods in normal fullterm infants show how the capabilities of the subcutaneous adipose tissue change appropriately to meet the varying needs of the infant during the first critical hours and days of life. We plan to investigate neonates with abnormalities of intrauterine nutrition, the prematurely born, the "small-for-dates" infant and the offspring of diabetic mothers, and also with fetal distress or hypoxia in the immediate perinatal period. The ability of these babies to utilize fat stores, and in some cases the amount of adipose tissue, may be faulty. If abnormalities can be related to disease states, it may prove basis for the prevention or treatment of complications in the perinatal period with subsequent reduction in perinatal mortality and morbidity.